In situ immobilization of metals within density variant bodies of water

ABSTRACT

A method for treating (in situ) large bodies of water contaminated with heavy metals and having varying density stratas to immobilize the contaminant metals is disclosed. The method, or process for (in situ) immobilization of metals is focused on treating large bodies of water having metals therein that are also adjacent a border of soil or earthen materials in an attempt to immobilize the metals from penetrating through the soil. The method is also able to treat the soil water boundary within the pit lake to provide additional immobilization. The pit lakes can include open pit lakes, subterranean mine lakes, flowing streams and the like. The method is also able to treat an abandoned mine prior to the filling of the mine with water. Initially, the density mean of the body of water is determined, which is densest typical at regions at or approaching 4 degrees C. The process includes introducing a treatment substance that has a density greater than that of the density means into the body of water, providing at least one microbe proximate or in the body of water, producing microbial sulfides arising from the initial microbe placement, causing microbial sulfides to react (in situ) with metal ions or metal containing compounds located within the body of water, reducing the solubility of the metal ions by forming metal sulfides, and inhibiting the migration rate of the metal ions or other metal containing compounds within or from the soils or earthen materials as they settle out of the water.

This application claims the benefit of PCT Application US01/31063, filedOct. 3, 2001, which is a Continuation-in-Part of U.S. application Ser.No. 09/678,272, filed Oct. 3, 2000, now U.S. Pat. No. 6,350,380; andSer. No. 09/678,527, filed Oct. 3, 2000, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to methods for in situ immobilization of metalsin water and earthen boundaries bordering the water as well as toimmobilization treatment of metals in water having varying density zonesto access and treat all regions within the water and at thewater-earthen boundaries.

Waste stacks are generated by many types of industrial processes, oftenas a result of the extraction of valuable materials. The waste stacksare frequently piles of economically invaluable material left over fromthe industrial processes. For instance, power plants often generatewaste stacks of ash. The ash is left over when energy is extracted fromfuel by burning. Mining processes also often generate waste stacks. Thewaste stacks contain minerals left over after a valuable metal ormineral is extracted from the mined earth materials. For example,phosphorus mines often result in waste stacks containing predominantlygypsum as a processed waste. The waste stack gypsum is a relativelyinvaluable mineral left over after phosphorus is removed from the minedmaterials.

In many instances, waste stacks are formed as follows. First, theresidual or waste material is combined with water to form a wasteslurry. This waste slurry is then flowed to a settling pond where thesolids contained in the waste slurry settle out. Water evaporates orpermeates from the settling pond. Over time, the settled solids leavebehind a stack of waste material. Some water is retained in the settledwaste material which makes up the waste stack. This process ofdeposition settling and evaporation is repeated until the resultingwaste stack is too large for the process to economically continue, or isterminated for other reasons. If needed, a new waste stack is startedand grows in a similar fashion. FIG. 1 shows a mine 12 which has been inoperation for a significant period of time and is surrounded by a numberof waste stacks 14. The individual waste stacks 14 are often huge,frequently comprising millions of cubic yards. The amount of materialcurrently stored in waste stacks is enormous, and it continues toincrease as mining and other industries continue to produce and developnew operations.

A problem associated with waste stacks is toxic metal migration. Theactual percentage of water-soluble toxic metals in a given waste stackis usually very small; for example, less than 1.0 percent. Because thewaste stacks are often very large, however, the total amount of toxicmaterials in a waste stack is often large enough to present some risk tosurrounding areas and ground water. These risks arise in part due topotential metals migration of liquids from the waste stack. The slurrywater may percolate into the soil in addition to evaporating orremaining in the waste stack.

Toxic metals potentially found in waste stacks include but are notlimited to Pb, Hg, U, Cd, Fe, As, Se, Cu, Cr, Ni, Zn, Co, Mn, and Ag.Over time such metals can leach out of the waste stacks and into groundwater. Thus, it is desirable to keep the metals within or near the wastestacks to minimize the danger posed by such metals.

Keeping the metals within or near the stack is often difficult,especially since the metals may be present in water-soluble forms. Suchwater-soluble forms can migrate as metal solutes whenever water movesthrough the stacks. Since the stacks are frequently exposed to water,either in the form of rain or in the form of wastewater deposited on thestacks, water-soluble metals or metal compounds present in the stacksare exposed to conditions that may encourage their migration. In somesituations, metals have already begun migrating out of existing wastestacks and into a boundary zone or layer below the waste stacks. Thus,it is desirable to have a method which will not only inhibit furthermigration of metals from the waste stacks, but which will also inhibitthe migration of metals that are in a boundary layer beneath the wastestacks.

One method for containing metals within a waste stack has been to treatthe waste stack with microbes that are capable of producing microbialsulfides. The microbial sulfides are sulfide byproducts of microbialactivity in waste stack affected zones. The microbial sulfides reactwith metal ions or metal containing compounds contained in the wastestack affected zones to form metal sulfides. The metal ions or metalcontaining compounds contained in the waste stack affected zones becomerelatively insoluble during this treatment and are inhibited frommigrating within or from the waste stack affected zone. This method wasfirst disclosed in U.S. Pat. No. 5,632,715, which is incorporated hereinby reference. This method has been applied successfully in treatingwaste stacks and inhibiting migration of metals within boundary areaswithin such waste stacks.

With the excavation of mining materials during the mining process, avoid is typically created that is often filled with water. These largewater-filled zones, typically known as pit lakes 15, contain many of thesame type of contaminants as are found in waste stacks, especially whenthe lake is adjacent a waste stack from the mining operation.Additionally, the pit lakes have soil boundaries along the surface aswell as extending down to the bottom of the lake. Metal migrationcontinues to occur within the soil boundaries between the water and thesoil. Further still, the water from the pit lakes can seep into adjacentwater tables, which can result in the contamination of water systems inpopulated areas.

One prior art method of treating such bodies of water has been to pumpthe water from the lake source to a process treatment plant and thenreturn the treated water to the pit lake. Another method in the priorart for treating such bodies of water has included taking the processtreatment plant to the body of water and placing it on a boat thattravels across the surface of the pit lake to treat the water at thesurface level and return the treated water back to the surface.

There are several problems that exist in either solution. Firstly, bothtreatment solutions are expensive to conduct, as the cost of pumping thewater alone can be extreme. Secondly, mixing treated water withcontaminated water only causes the contaminated clean water to bere-contaminated, or require there be a secondary storage facility, whichis not always available or suffers from the same soil contamination ofthe first pit lake. Thirdly, the plant operators must be on the water inthe process on the lake method, which potentially exposes the operatorsto the contaminated water unnecessarily. Fourthly, these treatmentsolutions are at times unable to reach the depths of these pit lakes,which can have depths ranging from 50 feet to as great as 3,000 feet.Again, water pumping becomes expensive for deep pit lakes. Fifthly,certain water-filled workings are completely subterranean and arevirtually impossible to access directly or the water is so deep thatpumping the water from the subterranean cavity to the surface fortreatment becomes cost prohibitive.

Not only must the water be treated in such conditions, but so to mustthe soil boundary within either the subterranean pit lake or the openbody pit lake also be treated during the treatment process. The priorart methods of removing the water for treatment at a separate location,or merely treating the water on the surface of the pit lake fails totreat to treat the soil boundary of the lake simultaneously withtreating the water.

Accordingly, there is a need within the industry to be able to treatcontaminated water sources, such as pit lakes and subterranean minecavities filled with water, in an economical and environmentally soundway that also includes treating the soil boundaries adjacent the water.

SUMMARY OF THE INVENTION

According to the present invention, an in situ method for treating largebodies of water having varying density strata to immobilize contaminantmetals within the water is disclosed. The method is also able to treatthe soil water boundary within the pit lake to provide additionalimmobilization. The pit lakes can include open pit lakes, subterraneanmine lakes, flowing streams and the like. The method is also able totreat an abandoned mine prior to the filling of the mine with water. Theinvention also contemplates treating bodies of water having varyingdensity strata.

The method, or process for in situ immobilization of metals is focusedon treating large bodies of water having metals therein that are alsoadjacent a border of soil or earthen materials in an attempt toimmobilize the metals from penetrating through the soil. Initially, thedensity mean of the body of water is determined, which is densesttypical at regions at or approaching 4 degrees C. The process includesintroducing a treatment substance that has a density greater than thatof the density means into the body of water, providing at least onemicrobe proximate or in the body of water, producing microbial sulfidesarising from the initial microbe placement, causing microbial sulfidesto react in situ with metal ions or metal containing compounds locatedwithin the body of water, reducing the solubility of the metal ions byforming metal sulfides, and inhibiting the migration rate of the metalions or other metal containing compounds within or from the soils orearthen materials as they settle out of the water. The treatmentsubstance typically includes at least one microbe nutrient to sustainactivity of the microbes added thereto. The microbial activity yieldsmicrobial sulfides that react with the contaminants within the water toform the metal sulfides.

The treatment can include more than one supplemental feeding of thetreatment substance and the treatment substance can be either in liquidor powder form, which dry powder form may include pellets ranging in thesize from one millimeter to 300 millimeters in diameter. The pellets, inlarger size form, can be processed to have an average density largerthan the density mean of the water so that the weigh of the pelletscarries them past the densest regions within the water and dissolve at arate suitable for dispersal of the treatment substance throughout thebody of water.

The treatment substance, or fluid, is also buffered so as to balance thepH of the water being treated within a range of 6 to 8 pH. Accordingly,the treatment substance includes a treatment fluid having a pH range ofabout 1 to 12 in order to buffer the water during application. Themicrobes that are relied upon to generate the microbial sulfides canalso occur naturally within the body of water or within the soils orearthen materials.

The treatment substance is also designed to specifically excludecysteine. The sulfides typically react with contaminant metals includingAS, SE, CD, HG, CU, CR, U, FE, ZN, PB, NI, CO, MN, and AG.

The treatment substance is further characterized to include aconcentration of a carbohydrates to serve as microbial nutrients. Thecarbohydrate has a concentration of up to 10 grams per liter of fluid tobe treated and can further include up to 0.1 grams of total nitrogen perliter of fluid to be treated. Further still, the treatment substance canalso include about 0.25 grams of phosphate ion per liter of fluid to betreated or a combination of carbohydrate, phosphate ion, and totalnitrogen. The phosphate can be adjusted by volume weight to carry thetreatment substance below the densest regions within the body of water.The treatment substance can also include buoyant agents that carry thenutrients from lower first regions to higher second regions after thetreatment substance reaches the first region, which is typically belowthe densest regions. This buoyant agent can be biologically derived,chemically derived, or be a gas, such as one selected from, but notlimited to, N₂, CO, CO₂, H₂, CH₄, SO₂, H₂S.

In an alternative embodiment, the treatment substance comprises one ormore alcohols and a carbohydrate, which can be selected from the groupof whey, corn syrup, or hydrolyzed starch. In the alcohol andcarbohydrate mixture, the treatment substance has generally a 3:1 ratioof alcohol to carbohydrate and can also include up to 30 mg. of totalnitrogen per liter of liquid to be treated. The microbe can be selectedto include one or more microbes selected of a genus coming from thegroup consisting of Desulfovibrio, Desulfomonas, and Desulfomaculum.

In another alternative embodiment of the present invention, a processfor in situ immobilization of metals within soils located within areservoir is disclosed that includes placing treatment substance andmicrobes within the soil prior to the addition of the water.Specifically, in the case where mines are back-filled with water afterthey have been closed, the treatment substance, whether dry or liquid,along with a microbe that generally produces microbial sulfides, isplaces at various locations within the mine at various elevations inorder to treat the mine for in situ immobilization upon filling of themine with water. Once the treatment substance and microbes are in place,then water begins to flow within the reservoir, which wets the soil andthe treatment substance and the microbe. The microbes become active andfeed upon the microbial nutrients within the treatment substance toproduce microbial sulfides. The microbial sulfides react in situ withmetal ions or metal containing compounds contained in the soil orotherwise soluble within the flowing water to form metal sulfides. Thisreaction causes the metal ions or metal containing compounds to bereduced in solubility and eventually precipitate out as metals sulfidesinto the soil or other earthen boundaries within the reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only typical embodiments of the invention and are,therefore, not to be considered limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 is a top view of a prior art mining area showing a minesurrounded by a number of waste stacks and a pit lake.

FIG. 2 is a sectional side view of a pit lake affected zone beingtreated according to a first embodiment of the invention. Treatmentliquids are being applied onto the surface of the pit lake.

FIG. 3 shows a sectional side view of a subterranean pit lake beingtreated according to a second embodiment of the invention. Microbenutrients are being flowed into the lake as accessed via a chamber.

FIG. 4 shows a sectional side view of an abandoned mine prior to backfilling with liquid and that is being treated according to a thirdembodiment of the invention. Microbe nutrients are placed at variouspoints within the mine to optimize treatment as the mine is filled withliquid.

FIG. 5 shows a sectional side view of an open pit lake having variousstrata of densification and being treated according to the presentinvention to account for the varying densities within the pit lake.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

It will be readily understood that the components of the presentinvention, as generally described and illustrated in the figures herein,could be arranged and designed in a wide variety of differentconfigurations. Thus, the following more detailed description of theembodiments of the system and method of the present invention, asrepresented in FIGS. 2 through 5, is not intended to limit the scope ofthe invention, as claimed, but is merely representative of theembodiments of the invention.

The specific embodiments of the invention will be best understood byreference to the drawings, wherein like parts are designated by likenumerals throughout.

FIGS. 2–5 illustrate selected forms of the present invention. Theseforms of the invention are expected to apply to the following situation.A pit lake 14 is provided over a subadjacent soil or other support earthmaterials 16. A water soil interface 18 results from where pit lake 14meets soil 16. Water soil interface 18 extends along a base 20 of pitlake 14. One or more water-soluble forms of one or more toxic metals,such as selected from the group consisting of Pb, Hg, Cd, Fe, As, Se, U,Cu, Cr, Ni, Zn, Co, Mn, and Ag exist within pit lake 14 and may berendered less mobile by the inventive process taught in accordance withthe present invention. Such toxic metal contaminants typically exist atrelatively low concentration levels, 0.001–1000 parts per million.

As shown in FIG. 2, a metal-containing boundary layer or boundary zone22 may also exist adjacent to pit lake 14. Metal-containing boundaryzone 22 may exist if pit lake 14 is exposed to a waste stack or othertailings zone that has water leaching toxic metals out of the wastestack and past the water soil interface 18, thereby forming metalcontaining boundary zone 22.

Pit lake 14, together with any present metal-containing boundary zone22, defines a water soil affected zone 24. In accordance with theprinciples of the present invention, a method is disclosed thatimmobilizes the toxic metals in situ within the water soil affected zone24 to inhibit substantial migration of these toxic metals and preventmovement of contaminants into an extended area 26.

In one form, the method includes utilizing the biological activity ofmicrobes to generate sulfides in pit lake 14, which treatment extendsthroughout the water soil affected zone 24. The microbially-producedsulfides, which are referred to herein as microbial sulfides, arecombined with toxic metals in the affected zone to convert the metalsinto metal sulfides. In one exemplary embodiment of the presentinvention, the microbially produced sulfides react with metals or metalions such as selected from the group consisting of Pb, Hg, Cd, Fe, As,U, Se, Cu, Cr, Ni, Zn, Co, Mn, and Ag. The toxic metals may be in theform of metal ions, metal ion complexes, or metal containing compounds.A possible mechanism for the conversion to metal sulfides, using thecadmium ion as an example metal ion, is:C₆H₁₂O₆+NAD+H+>>6CO₂+6H₂O+NADH  (1)10NADH+SO₄ ²⁻>>H₂S+10NAD+4H₂O  (2)H₂S(aqueous)+H₂O>>H₃O⁺+HS⁻(aqueous)  (3)HS⁻+H₂O>>S²⁻+H₃O⁺  (4)Cd²⁺+(aqueous)+S²⁻(aqueous)>>CdS(solid)  (5)

In the shown mechanism, NAD is nicotinamide adenine dinucleotide, whichis used ubiquitously in biological transport mechanisms.

Once metal sulfides, or other sulfided metallic forms, are formed, thecomplexed metals become relatively insoluble in water and tend toprecipitate out of the water and into the boundary 24. The metals arethereby held in the soil and boundary zone 24, preventing furtherwater-borne migration.

It is believed that a variety of microbes that generate appreciablequantities of sulfides can potentially be used in the treatment methodsof the present invention. For example, microbes of the generaDesulfovibrio, Desulfomonas and Desulfomaculum are known to generateappreciable quantities of sulfides as a by-product of their growth andgeneral biological activity. They are believed to be suitable for use inthe present invention. Three specific embodiments of the presentinvention will now be described in detail.

First Embodiment

As illustrated in FIG. 2, a first embodiment of the present inventioncomprises treating an open body of water known as pit lake 14 to delivera treatment solution with sustaining nutrients on the surface of pitlake 14. The effective treatment of the pit lake 14 along with the watersoil affected zone 24 requires a reasonable calculation of the volume ofwater found within pit lake 14 as well as the surface area of the watersoil boundary area 20. Further still, the present invention requires areasonable estimate of the amount of metal contaminants within theaffected zone 24 so that a reasonable calculation of the requiredmicrobial sulfide, with requisite nutrients, can be delivered to the pitlake 14 for treatment.

During the determination of the pit lake size and the boundary zonesize, the pH is measured in the water to determine if some areas arewithin a pH range of from about 3.0 to about 10. What is important isthat there be a potential biological activity zone wherein the microbialsulfides, along with their nutrients, can flourish for theimmobilization of the water soluble metals within the affected zones.

Once the pH has been determined to be sufficient enough to provide abiological activity zone, or the lake has been treated in such a way asto provide a temporary biological activity zone, a treatment liquid 30is introduced onto the surface of pit lake 14. Typically, a source isprovided from which treatment liquid 30 is sprayed onto the surface ofpit lake 14 and convection currents along the surface distribute theliquid across the entire surface and within the varying depths of thewater. The injection of the treatment liquid 30 can be eithermechanically delivered or gravity delivered.

Treatment liquid 30 is primarily constituted of a suitable liquid base,such as water. In addition to the water or other liquid base, there area number of additional constituents within the liquid. Treatment liquid30 also includes at least one microbe nutrient that is capable ofsustaining biological activity of at least one microbe. Specifically,treatment liquid 30 will comprise an appropriate nutrient supplementnecessary for microbes to grow within the water of open lake 14 as wellas at the affected zone 24 and produce sulfides. Such appropriatenutrient supplements are readily determinable by persons skilled in theart of microbial growth. Further, treatment liquid 30 should not containexcess nutritional supplements beyond what is necessary for the microbesto grow and produce sulfides. Such excess nutritional supplements wouldresult in economic waste, and potentially inhibit the anaerobicrespiration necessary to form sulfides. This form of inhibition iscommonly known as fermentation.

The particular concentration of microbe nutrient varies depending upon apre-determined bio-availability of nutrients and the chosen speed ofbiological activity for the given application. The concentration ofmicrobe nutrient also depends upon the particular nutrient that is beingemployed. The concentration of microbe nutrient also depends upon otheraspects of the particular pit lake 14 and adjacent boundary areas 24being treated. For example, the chemistry of a particular boundary area24 may be relatively less favorable or more favorable to microbialconversion of the nutrient, which requires that the amounts used areadjusted to effect microbial growth and sulfide production to immobilizemetals. An exemplary range of nutrient concentration is from about 0.1to about 10 grams of nutrient per liter of liquid 30.

In one form of the invention, treatment liquid 30 includes acarbohydrate microbe nutrient. Carbohydrate microbe nutrient is in theform of either molasses, hydrolyzed potato starch, whey from milk ormilk by-products, and whey from milk or milk by-products with theprotein fraction removed or substantially removed.

In another form of the invention, treatment liquid 30 includes acarbohydrate microbe nutrient. The microbe nutrient is typicallyselected from one of the following types of nutrients, includingmolasses, hydrolyzed potato starch, whey from milk byproducts, and wheyfrom milk byproducts with the protein fraction removed or substantiallyremoved. A list of microbe nutrients includes alcohols, partiallyhydrolyzed amylosk or celldosis fractions, aerosol gelling componentsenabling treatment of a shallow lake or other temporarily buoyantorganic sawdust or straw. The treatment liquid 30 is delivered as atreatment volume of generally 1 gram of treatment liquid for each literof liquid to be treated. The alcohol and carbohydrates are mixed in a3:1 ratio of alcohols to carbohydrates. About 30 milligrams of totalnitrogen per liter to be treated is also added to the treatment liquid.

In an alternative embodiment of the present invention, treatment liquid30 can include a carbohydrate microbe nutrient and a biologicallysuitable and utilizable nitrogen source. The nitrogen source is includedin amounts sufficient to provide concentrations within the treatmentliquid from about 0 to about 500 milligrams per liter, or on a moreconstricted range from about 5 to about 100 milligrams per liter of N.Further, in this exemplary embodiment of the invention, it isanticipated that the carbohydrate microbe nutrient includes sugars andalcohols in a concentration of about 1 gram per liter total carbohydrateand about 10 milligrams nitrogen per liter of liquid to be treated.

In another alternative embodiment of the invention, treatment liquid 30comprises a carbohydrate microbe nutrient, phosphate ions, and nitrogensource. Suitable sources of phosphate ions include sodium phosphate,potassium phosphate, ammonium phosphate and potentially otherphosphates. The phosphate ion is included in sufficient amounts toprovide concentrations in the treatment liquid from about 0.010 to about0.25 grams per liter of liquid, or contaminated lake water, to betreated, and up to 0.1 grams of total nitrogen per liter of fluid to betreated. Thus, the volume of liquid to be treated is determined, thewater is tested for contaminant types and concentrations for eachcontaminant intended to be treated, then the amounts of nutrient,phosphate ions, and nitrogen source are each determined for addition tothe lake depending upon the concentrations of contaminants.

In one specific embodiment of the present invention, the cysteinecontent of the microbe nutrient will be low. Cysteine can interfere withmicrobial production of sulfides. Accordingly, the cysteine content inthe treatment liquid is kept low or is actually excluded from treatmentliquid 30 so as not to inhibit the production of microbial sulfidesduring treatment.

Treatment liquid 30 also comprises a pH to oppose the pH of the surfaceof pit lake 14, relative to a neutral pH 7. Thus, if the surface of lake14 is alkaline, treatment liquid 30 is preferably acidic, also if thesurface is acidic, treatment liquid 30 is alkaline. Treatment liquid 30is buffered so as to improve formation of the temporary bio-activityzone of the treatment liquid within lake 14.

Sulfide producing microbes are known to generally grow best in anenvironment with a pH from about 4 to about 7. A region within soilwater boundary area 24 referred to herein as a biological activity zone.The pH and buffer capacity of treatment liquid 30 is adjusted such thatthe interaction of boundary area 24 creates a biological activity zonewithin water and soil boundary. Again, the method of this inventioncomprises providing at least one sulfide-producing microbe capable ofgrowing in the presence of treatment liquid 30. The microbe may beprovided before, after, or during the injection of treatment liquid 30,and is placed in proximity to the surface of pit lake 14 with treatmentliquid 30.

In one embodiment of the invention, the step of providing thesulfide-producing microbe comprises treating the surface of pit lake 14with at least one microbe. The microbe may be placed on the surface ofpit lake 14 prior to, subsequent to, or during the injection of liquid30 onto the surface of pit lake 14.

In an alternative embodiment of the invention, the step of providing thesulfide-producing microbe comprises mixing the microbe with treatmentliquid 30 and delivering the mixture onto the surface of pit lake 14 tobegin the in situ immobilization of contaminating metals within pit lake14.

In yet another alternative embodiment of the invention, the step ofproviding the sulfide-producing microbe comprises utilizing microbesalready existing within pit lake 14 before liquid 30 is administered.The pre-existence of microbes within pit lake 14 may be due to humanimplantation, air-borne dispersion, or natural conditions of the openpit lake 14.

In accordance with the present invention, the method can also comprisethe step of administering one or more supplemental feedings of treatmentliquid 30 onto the surface of pit lake 14. The supplemental feedings areadministered after at least one prior treatment of treatment liquid 30,and is typically provided after the sulfide-producing microbes havebegun growing. The supplemental feedings are provided to sustain thegrowth of the sulfide-producing microbes. The sulfide-producing microbeswill produce sulfides over a longer period of time when supplementalfeedings are provided. Such long-term generation of sulfides increasethe immobilization of the metal ions, and minimize losses of microbialnutrient due to fermentation. Since sulfides may eventually be displacedfrom the coordination sphere of the metal ions through equilibriumprocesses, the long-term generation of sulfides helps to insure thatsuch displaced sulfides are rapidly replaced or supplemented by othersulfides, as in the transition from pyrrhotite (Fe_(1-x)S) to pyrite(FeS₂) or marcasite.

Further, as an alternative to the use of a carrier liquid to deliver thenutrients and microbes to the affected zone, solid materials that arenot wet or liquid can be used instead. For example, the treatmentsubstance can be a powder of nutrients that is activated simply bycontact with the water in the pit lake. This powder can be dispersedusing air dispersal or air drop via aircraft. This is convenient alsowhen the lake is too remote for pumping trucks to access for directdelivery at the shore. The treatment substance can also be less refinedthan a powder, either in pellet or clump form. The pellets can range insize from 0.1 mm to 300 mm. It is understood that smaller sized pelletsor powders achieve a larger overall surface area that can react withinthe treated water. The larger sized pellets also serve as a time releasemechanism as well since the larger diameter pellets take longer todissolve than the smaller pellets or powder. Additionally, the treatmentsubstance when in liquid form can also be dispersed aerially viaaircraft when border delivery is not possible.

Second Embodiment

FIG. 3 illustrates a second embodiment of the present invention wherethe body of water is actually a subterranean lake within the cavity ofan abandoned or existing mine. Subterranean lake 44 also includes anaffected soil water boundary area 28 like that of FIG. 2. The waterwithin subterranean lake 44 is treated using a water treatmentcomposition 46. Treatment composition 46 permeates the water in lake 44.One or more delivery chambers 48 are formed in the top surface of thesoil 52 above lake 44. These chambers 48 are placed at several locationsto provide a uniform dispersion of treatment liquid 46 within lake 44.These chambers are formed using conventional drilling techniques knownto those skilled in the art or are previously formed tunnels or shaftsformed during the mining operations. Natural caves and tunnels can alsoserve as delivery channels for the treatment composition. Next, thetreatment composition 46 is then delivered into lake 44 either viamechanical feed or gravity feed. The composition of treatmentcomposition 46 is similar to that of treatment liquid 30 describedabove.

There are three types of subterranean lakes that need to be considered.These lakes include a static lake, a sinking lake, and a gaining lake.The static lake has a constant volume that is either constant because ofno inflow and outflow, or is constant because there is a steady inflowmeeting the same rate of outflow. In either event, the volume of thewater stays relatively constant. The sinking lake is one where theoutflow rate exceeds the inflow rate and is draining at a given rate.The gaining lake is one where the inflow rate exceeds the outflow rateand therefore the volume continues to increase. It is important to knowwhat type of lake is to be treated as it is important to attempt totreat the lake at the locations as close to the inflow sources aspossible so that the treatment composition can permeate throughout thewater and affect the soil boundaries within the water as thoroughly aspossible. Should the treatment composition be added in an outflowingregion, then the treatment would occur along the path traveled by theoutflowing stream and not affect the general body of water upstream fromthe outflow region. Thus, placing treatment composition nearest theinflow sources helps to distribute the treatment composition within thebody of water in a manner most effective in providing in situimmobilization.

Thus, for gaining lakes, sinking lakes, and static lakes that have aconstant inflow and outflow, addition of treatment composition at thepoint of input increases the chances of distributing the treatmentcomposition throughout the water zones occupied in the abandoned mine.Accordingly, the chambers 48 are placed at locations as close aspossible to the source of inflow into the subterranean cavity.

In static bodies of water where there is no inflow or outflow, there islittle problem of contamination or a requirement that in situimmobilization be performed; however, in the event a breech occurs thatallows the water to flow out of the underground pit, treatment a prioriprevents mobilization of contaminate metals in accordance with thepresent invention. The process of performing in situ immobilizationwithin such bodies of water is also accomplished within one or moreembodiments of the present invention. Specifically, the treatmentcomposition 46 can be introduced within a static body within a carrieragent that can generate a gas phase atmosphere of nitrous that carriesthe reducing agent within all parts of the chamber. Testing of the watersample is necessary in order to determine whether the water has reacheda saturation level where nitrous would not diffuse within the water forone. Thus, it is contemplated that the treatment composition would beprepared in such a manner as to have a density greater than that of thebody of water to which it is introduced. This greater density allows thetreatment composition to settle near the bottom or in other locations atpoints lowest areas to be treated such that during the gas phasetransition, or the transition from a liquid or solid composition into agas-based carrying agent, the gas phase would introduce and lift thereducing agent upward and outward.

The method of the present invention may further comprise a step ofproviding one or more supplemental feedings of microbe nutrient intoaffected zone 44 using one or more additions of pool treatmentcomposition 46. The supplemental feedings should be flowed onto thestack after at least one prior feeding of microbe nutrient, andpreferably after the sulfide-producing microbes have begun to grow. Thesupplemental feedings are provided to sustain the growth of thesulfide-producing microbes. It is anticipated that the sulfide-producingmicrobes will produce sulfides over a longer period of time ifsupplemental feedings are provided. As discussed previously, long termgeneration of sulfides is advantageous for maximally immobilizing metalions.

It is intended in the present invention that the treatment of the largevolume of water either in the open pit lake or in a subterranean pitlake that the microbial sulfides eventually interact with the soilboundary between the soil and the water such that in situ immobilizationof contaminant metals at such soil points is obtained. For example, asthe microbial sulfides increase due to the nutrients added, they filterthroughout the water zone of the pit lake neutralizing soluble metalswithin the water. Further, they migrate towards the borders of the soiland are utilized to provide in situ immobilization of the water solublemetals located within the soils. Supplemental feedings encourage thegrowth of such sulfide producing microbes such that within a shortperiod of time, on the order of one to four months. The supplementalfeedings are continued until test samples of the water show a reducedlevel of contaminants, and that the soils adjacent the water also show agreatly reduced level of contaminants being treated.

Third Embodiment

FIG. 4 illustrates a third embodiment contemplated within the presentinvention. This particular embodiment relates to the anticipated fillingof a mine to be closed. At this point, there is no water of significantvolume within the mining cavity. It is recognized that the soilboundaries within the mine are contaminated and it is useful toimmobilize the heavy metals to prevent their immobilization out of themine and into adjacent water tables or soil boundaries. Further, it isdesirable to treat the water that also carries the heavy metals andimmobilize them as early as convenient as possible. Accordingly, as isillustrated in FIG. 4, an abandoned mine is illustrated.

Mine 100 has a cap head 102 located at an outer opening above a surfaceopening of the mine. A main shaft 104 is illustrated penetrating from atop surface downward to a lowest horizontal shaft 106 that was used toexcavate material from within the mine 100. Additional mining shafts ina horizontal plane are illustrated as shafts 108. Mine veins 110 arealso illustrated that typically provide a passage from open shaft 104 tothe outer surface of the mine. These veins 110 typically are sealed toprevent seepage or leaking or evacuation of material from within themine.

Since mine 100 is to be filled with water, treatment of the mine priorto filling is done in accordance with the present invention.Specifically, mine 100 is treated by placing nutrients throughout theabandoned mine prior to filling the mine with liquid. The nutrients areconsistent with those described above that encourage the growth ofsulfide producing microbes as defined and described within the presentinvention. These locations are placed in the mine at different stages inadvance of water penetration during the filling of the mine. Forexample, a first nutrient 112 is located in excavation shaft 106.

Nutrients 112 are placed at the lowest level so that as the water, whichtypically finds its lowest level during filling, will activate thenutrients and the microbes to begin the growth of the sulfide producingmicrobes to reduce the metal contaminants for in situ immobilization.Additional nutrients and microbes 112 are located at various otherpositions within the mine as identified at sites 116, 118, 120, and 122.Thus, as the water level rises, the water reaching a particular nutrientpackage activates the nutrient package to produce the sulfide producingmicrobes. This enables the mine to be treated not only incrementally asthe water fills, but also completely as the soil boundaries are wettedand begin releasing the contaminated metals within the water.

Thus, it has been taught to treat a mine or cavity in advance of itsfilling with water as a way of minimizing any metal mobilization withinthe soil boundaries or the water.

Fourth Embodiment

The method for treatment of large bodies of water disclosed includes theaddition of biological or chemical reagents to a lake surface anddistributed to various depths. The reagent dosage at depth is controlledby the several parameters: reagent density, droplet size andmiscibility. Large bodies of water, such as open pit lakes, are subjectto the seasons with the various weather changes they bring. The lakesare subject to freezing during the winter and warming well abovefreezing during the summer. These temperature extremes, along withnaturally occurring and varying wind forces, lead to stratification ofthe water into different density regions as shown in FIG. 5. Inaccordance with principles of the present invention, a method isdisclosed to enhance the distribution of reagents to perform a specificchemical transformation without the need for further mechanical mixingregardless of the varying density regions found with a subject pit lake.

FIG. 5 illustrates a side view of a pit lake 14 having a depth D and animmobilization boundary 22. Lake 14 has a maximum density region M,which is determined by temperature sampling of the lake at varyingdepths. The colder the water, the denser the water becomes until 4° C.Thus, where the temperature is noted to be approximately 4 degreesCelsius at level M, the maximum density of the water is obtained. Theremay be varying levels of strata, but in this example, the M level is themost dense. As such, the treatment composition needs to be designed topenetrate this density level only, since it is the maximum density.

One example of the treatment composition utilized to perform in situimmobilization of contaminant metals in accordance with the presentinvention comprises in large part sugar syrup, which has a density of 11lbs/gallon, and alcohol (methanol or ethanol), which has a density of6.6 lbs/gallon. The sugar syrup and alcohol are blended continuously bysetting the flow rate of the controlling constituent, in this examplealcohol, and then modulating the flow of the densifying constituent inorder to achieve a suitable density that exceeds the Maximum density ofany strata level within lake 14. The densifying constituent has agreater variance from the desired mean density, thereby controlling themaximum or ultimate settling depth within the lake. In addition, boththe miscibility and the solubility of these constituents is varied toaccomplish the same effect. Alternatively, the density needs only exceedthe mean density of the lake since the composition will itself havedenser portions that reach through the densest strata levels of thelake.

A deep pit lake, such as created in mining operations for copper, goldor other minerals, is exposed to yearly freeze/thaw variation andmoderate fetch (wind force) that stratifies the water into differentthermally defined layers. The addition of a nutrient within thetreatment composition to enable bio-reduction along a givenelectro-potential series to re-mineralize metallic species or to removeother contaminants effectively treats only one layer of the lake sinceit poorly mixes with the other layers. Further it is likely to beunsuccessful in meeting regulatory requirements due to re-oxidation(half reaction couple 1 and 2) before useful consumption in the desiredhalf reaction couple 1 and 3:CH₃OH+H₂O=CO₂+6H⁺ +6e ⁻  Rxn 1:4H⁺+O₂+6e⁻=H₂O 1+2: Methanol+Oxygen=CO2 and Water.  Rxn 2:SeO₄ ²⁻+8H⁺+10e⁻=Se⁰+4H₂O 1+3: Methanol+Selena=CO2Se  Rxn 3:Since these reactions are biologically catalyzed, the addition ofphosphate, which has a density of 14.2 lbs/gallon, provides anotherdegree of control of delivery depth and enhance biological growth.

An alternative method of enhancing mixing is through biological orchemical generation of a gas such as nitrogen from reduction of nitratesas in coupling reaction 1 to reaction 4:2NO₃ ⁻+12H⁺+10e⁻=N₂+H₂O.  Rxn 4:Rising gas bubbles serve to carry excess settled sugars and reducedgases such as sulfide toward the surface and react with reducibleoxidized species along the way. This enables the treatment compositionto extend to the water/soil or earth interface immobilization zone asdescribed above to store reductive nutrients for future treatment ofspecies mobilizing from the pit high walls as well as all points betweenthe zone and the surface of the lake.

The invention has been described in language more or less specific as tostructural and methodical features. It is to be understood, however,that the invention is not limited to the specific features shown anddescribed, since the means herein disclosed comprise preferred forms ofputting the invention into effect. The invention is, therefore, claimedin any of its forms or modifications within the proper scope of theappended claims appropriately interpreted in accordance with thedoctrine of equivalents.

1. A process for in situ immobilization of metals in a body of waterhaving metals therein and having a border of soil or earth materials,comprising: introducing a solid treatment substance into the body ofwater, the treatment substance including at least one microbe nutrientto sustain activity of at least one microbe; providing at least onemicrobe proximate to or in the body of water to receive the treatmentsubstance therefrom, the at least one microbe being capable of growingin the presence of the treatment substance; producing microbial sulfidesthat are sulfide by-products of microbial activity in the body of water;reacting the microbial sulfides in situ with metal ions ormetal-containing compounds contained in the body of water to form metalsulfides; reducing solubility of the metal ions or metal-containingcompounds contained in the body of water as a result of forming themetal sulfides; inhibiting the migration rate of metal ions ormetal-containing compounds within or from the soils or earth materials;and varying at least one of a particle size and a density of the solidtreatment substance to thereby control a release rate of the at leastone microbe nutrient from the solid treatment substance to therebycontrol the production of microbial sulfides.
 2. A process according toclaim 1 wherein the step of introducing a treatment substance is furthercharacterized by the at least one microbe nutrient including acarbohydrate microbe nutrient.
 3. A process according to claim 1 whereinthe process further comprises a step of introducing one or moresupplemental feedings of treatment substance.
 4. A process according toclaim 1 wherein the step of providing at least one microbe includesrelying upon natural microbes which exist in the soils or earthmaterials.
 5. A process according to claim 1 wherein the step ofreacting the microbially produced sulfides comprises reacting themicrobially produced sulfides with at least one metal selected from thegroup consisting of As, Se, Cd, Hg, Cu, Cr, U, Fe, Zn, Pb, Mn, Mo.
 6. Aprocess according to claim 1 wherein the step of introducing a treatmentsubstance is done using a treatment substance which is sufficiently lowin cysteine content so that the at least one microbe are not inhibitedfrom producing microbial sulfides.
 7. A process according to claim 1wherein the step of introducing a treatment substance is furthercharacterized by a treatment substance which achieves a concentration ofup to 10 grams of carbohydrate per liter of fluid to be treated.
 8. Aprocess according to claim 1 herein the step of introducing a treatmentsubstance is further characterized by a treatment substance thatachieves a concentration of up to 10 grams of carbohydrate per liter offluid to be treated and up to 0.1 grams of total nitrogen per liter offluid to be treated.
 9. A process according to claim 1 wherein the stepof introducing a treatment substance comprise introducing and flowing atreatment substance that achieves a concentration of up to about 10grams of carbohydrate per liter of fluid to be treated, up to 0.25 gramsper liter of phosphate ion and up to 0.1 grains of total nitrogen perliter of fluid to be treated.
 10. A process according to claim 1 whereinthe step of introducing a treatment substance is further characterizedby a treatment substance that comprises of molasses, whey, corn syrup,hydrolyzed starch, other carbohydrate laden liquids and alcohols.
 11. Aprocess according to claim 1 wherein the step of introducing a treatmentsubstance is further characterized by a treatment substance thatcomprises approximately of 1 gram of treatment substance per liter offluid to be treated, in a ratio of 3:1 alcohols to carbohydrates, andapproximately 30 milligrams per liter of total nitrogen.
 12. A processaccording to claim 1 wherein the step of providing at least one microbecomprises providing one or more microbes of a genus selected from thegroup consisting of Desulfovibrio, Desulfomonas and Desulfomaculum.